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CARBONIFEROUS LIMESTONE OF STEERAWAY, ETC. 



field ; and which contain seams of coal and courses of ironstone almost to the very 

 base of the arenaceous strata. These arenaceous strata rest in several localities upon 

 the true carboniferous or mountian limestone. As this limestone, however, has no great 

 range, and is not of large dimensions, the coal-field throughout the greater part of its 

 extent, reposes at once upon other and older rocks, chiefly of the Silurian System, and 

 in the southern district upon Old Red Sandstone. (PL 29. fig. 11.) The carboniferous 

 limestone rises from beneath the coal measures at Little Wenlock, to the north-west of 

 which this limestone appears at Oldfield works, and ranging thence by the Hatch Bank 

 to Steeraway, extends in a narrow ridge from south-west to north-east, nearly two 

 miles in length. This limestone dips to the south-east at an angle of about 45° in the 

 principal works at Steeraway, where it is burnt for lime. (See section PL 29. fig. 16.J 

 The beds, eight in number, have an aggregate thickness of eleven yards, but vary indi- 

 vidually from five inches to twenty-six each, and are associated with strata of impure 

 limestone, shale, &c, amounting in all to upwards of one hundred feet. The limestone 

 is of a very dark grey, almost black, colour, in which respect, and in being very thick- 

 bedded and not of concretionary structure, it is quite unlike the Wenlock limestone of 

 the underlying Silurian System. The distinction between these limestones is rendered 

 still more complete by the organic remains, which are in great profusion at Steeraway, 

 consisting of shells and corals which are characteristic of the carboniferous limestone 

 in many other parts of Great Britain, and never occur in the inferior limestones of the 

 Silurian System. Among these the most prominent are the large Productus hemisphce- 

 ricus and many corals, including Lithodendron seosdecimale, Phillips, (Cladocora, of 

 Ehrenberg,) which is so abundant, that it constitutes massive beds, particularly the 

 layers of black calcareous shale, which divide the limestones. This black limestone of 

 Steeraway is overlaid by a sandstone, which separates it from the productive coal beds, 

 and is underlaid by strata belonging to the lower limestone shale, consisting of lightish 

 yellow sandstone, with layers of impure limestone and shale, which are interposed be- 

 tween it and the trap rocks of the Ercal and the Wrekin. 



All this portion of the edge of the coal-field is much convulsed, trap rocks intruding at many 

 points, so that a patch of the limestone is found adherent to the trap in the village of Little Wen- 

 lock, and the mass at the Hatch Works is quite broken off from that of Steeraway. (See Map and 

 PI. 29. fig. 16.) Limestone, similar to this of Steeraway, was discovered below the productive 

 portion of the adjoining coal-field at Lawley, distant upwards of one mile from the natural outcrop 

 of the rock. It had apparently thickened upon the dip and had become much less inclined. This 

 underground mass was extracted for some time, but the works are now abandoned. The north- 

 western edge of the coal-field is marked by a powerful downcast fault extending from the end of the 

 Steeraway and Ercal Hills to Lilleshall, by which all the lower strata are lost, the productive coal 

 measures abutting against the New Red Sandstone for a distance of nearly five miles. Along this 

 line the coal measures plunge to the north-west, unlike those at the edges of the coal-field at Steer- 

 away, Little Wenlock, and the Iron Bridge, where they dip to the south-east. It has, however, 

 been ascertained by Mr. Prestwich that this north-west dip is only partial, and that the coal strata 



